Contact copy correcting sheet and method of using



R. J. Ful-:RST 3,170,807

CONTACT COPY CORRECTING SHEET AND METHOD 0F USING Feb. 23, 1965 Filed May 16, 1962 United States .Patent 3,170,807 CONTACT COPY CRRECTENG SHEET AND METHOD F USING Robert il. Fuerst, White Plains, N.Y., assigner to Kores Manufacturing Corporation, New York, NX.

Filed May 16, 1962, Ser. Nrn-195,289 3 Claims. (Cl. 1175-2) cop-ies made with carbonless copy paper s uch as the copy paper described in application, Serial No. 136,711. Carbonless copy paper may be used, for instance, in the form ofasheet assembly composed of a plurality of sheets, one. of which is provided on one face with a transfer layer` which is adapted to be placed in face-to-face contact With another sheet carrying on its contacting face a takeup layer, the transfer layer consisting essentially of a resinous substance selected from the group consisting `of polyvinyl acetate7 mixed polymerizates of polyvinyl ace,

tate, colophonium, polymethylacrylate, .polymethylmethacrylate, polycarbonates, polystyrene, polychloroprene,A

styrene-butadiene t copolymers, cumarone resins, and cumarone-phenol resins in an amount of about 4-20% by weight of the transfer layer, of at least one plasticizer for the resinous substance, of at least one organic xing agent selected from the group consisting of tannic acid, gallic acid, digallic acid, salicylic acid, phenyl sal-icylate, 4 butyl-phenyl-salicylate, 5-chloro-2-hydroxy-benzophenone, 2,4-dibenzoyl-resorcin phenol and pyrogallic acid, of at leastlone inorganic substance of substantially colloidal particle size and selected from thesgroup consisting of bentonite, kaolin, calcium carbonate, calcium sulfate, calcium phosphate and zinc oxide, and of a pigment; and the take-up layer consisting essentially of a dry resinous substance selected from the group consisting of acrylic polymers, vinyl polymers, acrylic-vinyl mixed polymers, poly,-

diolefnes, dioleline-styrene mixed polymers, polycarbonates, colophonium, copal, abietic-maleic resin and cumaron res-ins and of at least one plasticizerin which the resinous substance is soluble, preferably in' an amount of 10-50% Yso by weight of the/weight of the resinous substance. The s composition of the variouslayers is described in'more detailin the above-mentioned U.S. patent application, Serial No. 136,711.

The diiiiculties encountered in theuse of this assembly include that the resulting copy cannot be removed neatly With an ordinary eraser. Furthermore, the coating of the reverse side of the original, ie., the transfer, layer is removed completely at those portions Where pressure is applied "and the corresponding portion of the transferV layer is adhered to the take-up layer of the underlying sheet, and therefore no reproducing medium is left at such depleted portion of the transfer` layer for use upon subsequent and repeated exertion of pressure to form a corrected copy onthe take-upV layer. v e t It is therefore an object of the present-invention to provide` a correcting sheet and method -for correcting copies produced, for instance, with such lsheet assemblies as described above, in such a manner'that the incorrect f copy, for instance a typographical error, can be removed and a correct copy can be produced in place of the removed incorrect copy. i

Itis a further-,object of thepresent invention to achieve ICC manner.

Other objects and advantages of the present invention will become apparent from a further reading of the description and of the appended claims.

With the above and other objects in View, the present invention contemplates for use in an assembly for correcting contact copy of the type formed by placing one sheet which is provided on one face With a transfer layer having a rst color in face to face contact with another sheet Which is provided with atake-up layer having a second color contrasting with the first color, with the transfer and Ytake-up layers contact-ing each other,and applying pressure to spaced portions of the other face ofthetone sheet so that corresponding portions of the transferlayer thereof will be transferred onto the take-up layer of the other sheet, in combination, a correcting sheet comprising a carrier sheet provided on one face, thereof with a lirst layer of substantially the iirst color adapted upon application of pressure to adhere to the transfer layer of the first sheet, and also adapted to besubsequently transferred by application of pressure from the rst sheet to the take-up layer of another sheet, and provided on its other face with a second layer of substantially the second color and adapted upon application of pressure to adhere to the take-up layer of the second sheet forming part there-y of, whereby upon interposition of the correcting sheet between the one and the other sheet with the tirst layer of the correcting sheet contacting the transfer layer of the first sheet andthe second layerof the correcting sheet contacting the take-up 'lay-er of the second sheet and application of Apressure to the spaced portions of the thus formed sheet assembly the portions of the faces of the first and second sheet to which the spaced pressure is applied will be covered by corresponding portions of the respective layers ofthe correcting sheet.V t The present invention is also concerned With an assembly for correctingjcontact copy of the type formed by placing one sheet whichis provided on one face with a transfer layer 'in face to facecontact withtanother sheet which is provided with a take-up layer, and the transfer and take-up layers contactingeach other, and applying pressure to spaced portions of the other face of the one sheet so that corresponding portions of the :transfer layer thereof will be transferred onto thel take-up layer ofthe other sheet, in combination, a first sheet provided on one face Withthe transfer layer, va ,second sheet provided ononeface with a take-up layer,`, the first andsecond sheets beingsuperposed with` the transfer Iand take-up layers adjacent to each other, and a correcting sheet interposed between the superposed rst and second sheets, the cor- -recting sheet comprising a carrier sheetprovided on oneV face thereof with a iirst layer adapted upon application of pressure to adhereto the transfer layerof the rst sheet,

The present invention further comprises in a method v'of 'correcting contact copy' of the type formedby placing one sheet which is provided on one face With a transfer layer in face to face contact with another sheet which is provided With a take-up layer, with the transferV and takeup layer contacting each other, and Iapplying pressureto t spaced portions of the otherlface of the one sheet'so that corresponding portions of the transfer layer thereof will be transferred onto the take-up layer of the other sheet forming copy thereon, the steps of interposing between superposed transfer and take-up layers having lthe copyv` A formed on the take-up layer Ia correcting sheet carrying on Patented Feb.` 23, 19655 of the second sheetfthe one face of the interposed corone face a transfer layer and on the other face a take-up layer, with the take-up layer of the correcting sheet facing the copy formed on the take-up layer of the other sheet and the transfer layer of the correcting sheet facing the transfer layer of the one sheet, and'applying spaced pressure corresponding to the configuration of the copy to the first and second sheet `with the correcting sheet interposed therebetween so that portions of the transfer and take-up layers of the correcting sheet corresponding to the copy will be transferred to corresponding portions of the transfer and take-up layers-carrying faces of the one and of the other sheet, respectively, thereby obliterating the previously formed copy thereon and restoring the transfer and take-up layers of the one and of the other sheet to their previous condition.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. l (comprising FIGS. 1a and 1b) is a diagrammatic, cross sectional illustration of the transfer of copy, using copy sheets of the type mentioned above, which copy may be corrected in accordance with the present invention as illustrated in the following figures of the drawing.

FIG. 2 illustrates a portion of what is shown in FIG. lb, namely, the copy sheet 1, 2 and the copy sheet 3, 1', 2 in the condition in which these sheets are shown in FIG. 1b, i.e., after copy has been transferred from sheet 1, 2 to intermediate copy sheets 3, 1', 2';

FIG. 3 illustrates the interposition of a correcting sheet according to the present invention between the two sheets shown in FIG. 2, and

FIG. 4 illustrates how repeated application of the pressure which formed the copy as shown in FIG. 2, however, with the correcting sheet interposed between the two sheets of FIG. 2 will correct, i.e., obliterate the copy which had been formed according to FIGS. I and 2.

Referring now to the drawings, and particularly to FIG. 1, the same illustrates the making of copies with three copy sheets. Copy sheet 1, 2 comprises a carrier sheet 1 and a transfer layer 2. It is placed adjacent a copy sheet 1', 2', 3, which comprises a carrier sheet 1', having on one face thereof a take-up layer 3, and on the other face thereof a transfer layer 2'. Sheet 3, 1', 2-' is placed between sheet 1, 2 and a further copy sheet 1, y3" comprising a carrier sheet 1" and a take-up layer 3". This assembly of three sheets is placed against the typewriter roller 6 and when the typewriter keys 7 and 8 strikes the sheet, the corresponding portion of the transfer layer 2 will be adhered to take-up layer 3 of intermediate copy sheet 3, 1', 2 and the corresponding portion of transfer layer 2 from intermediate copy sheet 3, 1', 2 to carrier sheet 1", 3", where it adheres to take-up layer 3".

For illustrating the present inventionV it will suffice to show in FIGS. 2, 3 and 4 only two copy sheets, namely sheet 1, 2; and the adjacent sheet 3, 1', 2.

According to FIG. 3, a correcting sheet 10, 11, 12, is interposed between the two sheets of FIG. 2.

Correcting sheets 10, 11, 12 comprises a carrier sheet 11, having -a transfer layer 10, facing the remaining portions of transfer layer 2 which adheres to carrier sheet 1, and carrier sheet 11 carries at its opposite face a take-up layer 12 which faces take-up layer 3 of the sheet comprising take-up layer 3, carrier sheet 1 and transfer layer 2', whereby it must be noted that now portions of transfer layer 2 forming the copy on sheet 1 adhere to takeup layer 3.

Upon striking the first sheet in the same manner as described in connection with FIG. lb, the portions of transfer layer 10 of the correcting sheet which are thus exposed to pressure will separate from the correcting sheet and will be adhered to carrier sheet 1 so as to fill the voids in transfer layer 2 which were formed upon initial exertion of pressure in accordance with FIG. 1b. Simultaneously, portions of take-up layer 12 which are exposed to pressure will Vseparate from carrier sheet 11, of the correcting sheet and will be superposed upon the portions 2 of the initial transfer layer 2 which upon originally exerting pressure were adhered to take-up layer 3 of carrier sheet 1'.

In this manner transfer layer 2 on carrier sheet 1 is restored and will consist now of the residual portions of the original transfer layer 2 and the fill-in provided by portions of transfer layer 11, while the copy formed on take-up layer 3 of carrier sheet 1 and which consisted of the portions of transfer layer 2 which upon initial exertion of pressure had separated from carrier sheet 1, will be made invisible by superposition of portions of take-up layer 12, preferably having a color similar to the color of take-up layer 3.

Upon subsequent removal of the correcting sheet 11 with the portions of layers 10 and 12 which were not subjected to pressure still adhering thereto, the carrier sheet 1, with transfer layer 2-10 thereon and the carrier sheet 1' with take-up layer 3-12 thereon, are freed of any previously produced copy, and the sheets which are still in the typewriter may be imprinted again by operation of the typewriter keys.

While, as illustrated, only the interposition of one correction sheet between two carrier sheets 1 and 1 with the respective layers thereon has been shown and described, it is of course possible to interpose a plurality of correction sheets between a correspondingly greater number of carrier sheets which, in `the illustrated sequence, carry on one face a transfer layer and on the other face a take-up layer. The bottom sheet need not carry a transfer layer at its face contacting the roller of the typewriter, and the top sheet need not carry a take-up layer at its face which will come in direct contact with the typewriter keys.

Thus, according to the present invention the correcting sheet comprises a carrier sheet of paper or other suitable medium which is coated on one side with a surface layer having substantially the same color as the take-up layer of the copy sheets, generally a white layer, and on its other side with a transfer layer which preferably will be dark grey or black, again corresponding to the color of the transfer layer of the copy sheets.

Again assuming that copy was produced in a typewriter and that a typographical error has been made, such error is corrected in the following manner: the correcting sheet is inserted between the original and the first copy sheet or, if there are more copies than the original and the first copy, other correcting sheets are inserted between the first and second copy sheet, and so forth, whereby each correcting sheet-is inserted in such a manner that its white surface, i.e., its take-up layer faces the take-up layer of the respective copy sheet. In other words, the white or take-up layer of the correcting sheet faces away from the typewriter keys, while the grey or black, transfer layer of the correcting sheet faces towards the typewriter keys, and thus towards the transfer layer of the adjacent copy sheet. The typographical error is now repeated at the identical location. As a result, the white surface of the correcting sheet releases a white pigment which will cover or obliterate the error appearing on the copy in grey or black or whatever other contrasting copy is used for the transfer layer, while at the same time portionsl of the grey or black or otherwise contrastingly colored transfer layer on the correcting sheet will be released therefrom and will cover the portion of the adjacent carrier sheet of the copy sheet from which the transfer layer previously had been removed by initially producing the typographical error.

Thereafter, the correcting sheet is removed from between any two adjacent copy sheets and between the original and the rst copy sheet, and it is apparent that the' layer of the correcting sheet.

It is of course possible toerase in conventional manner original image produced on the top sheet by direct pressure contact with the typewriter ribbon.

The correcting sheet according to the present invention thus will consist essentially., of a carrier sheet having on one face a preferably white layer which will be capable of covering the previously formed image on the copy sheet and having on its opposite face a layer 'which is adapted to restore the transfer layer of the original sheet or of a copyV sheet by transferring `transfer layer material to those portions of the carrier sheet of the original or copy sheet from which transfer layer had been removed by the previous typing action.

The take-up layer of the correcting sheet which generally will be of white color will consist of suitable pigments, binders and softeners. Minorv variations of the proportions of binder .and softenerfrelative to each other will produce very considerable variations in the hiding power or covering effect which transferred portions of the take-up layer will have relative `to theI underlying imprint.

The following examples of correcting sheets accord- Y ing to the present invention are. given as illustrative only,

without, however limiting the inventionto the specific details of these examples.

By using as carrier sheet of the correcting sheet a strongly calendered and glued paper, or a paper of the artificial parchment type, i.e., a paper which has very little absorptivezcapacity, it is possible to produce. clearv and sharp edged corrections with a relatively small percentage amount of lsofteners such as butyl Cellosolve, Palatino1,.Myverol or Cereclor. Pergamyn is a greaseproofimitation parchment paper made from sulfate pulp; Myverol is a glyceride derived from lard; Cereclor is a chloroparain containing 42% of chlorine, Cellosolve .broadly is,2ethoxyethanol; the Palatinol'softeners are phthalic acidderivatives well known in the art. n'

When the carrier sheet and the correcting sheet consist of'only slightly calendered and slightly glued paper, then the percentage of softeners must be increased.

The usually black or dark grey transfer layer of the correcting sheet which will .serve to regenerate the transfer layer. of the-copy sheets and thus to permit again to produce copy from` portions thereof vwhich previously had beensubjected to pressure,mayi`be chosen from variou-s groups .of' materials.

However, in this connectionitis important, thattheV adherence ofthe transfer layer` of the correcting sheets tothe carrier sheet must be somewhere in-between the degree of adherence of the transferlayer and of the takeup layerV of the copy sheets which are to be regenerated.

It isvtherefo're desirable, to adjust the specific composition of the transfer layer aswell-as of the take-up layer of the correcting sheets to the type of paper or the like which forms the' carrier sheet of the correcting sheet. Example Iy' i y The` correcting sheet comprises, a, carriernsheet of smooth calendered or artificiall parchmentfpaper weigh- -ing between 35 and` 40 gr. /m4.2.. L. D The white or take-up layer is producedby mixing: 37.50 parts-by weight'titanium dioxide 13.50 parts by weight lithopone (80%v zinc sulfide) `*27 parts by weight Furnex 50 i 6 2.10 partsby Weight Cereclor A42 (chloroparain 42% chlorine) i 1.05 parts by weight Myverol 18- 07 (glyceride of hydrated lard), n i .0.80 part'by weight Palatinol AH- (diocthlphthalate) 20.80 parts by weight ethanol 94% 0.04 part by weight Mark II A (a colloidal' carbon for use in inks, produced by Columbian Carbon Company,

The thus formed mixture isgroundfforone hour in a ball mill and thereafter the following solution'is admixed under stirring: f i

The amount of the thusV formed mixture which is applied to the carrier sheet depends on the quality of the carrier sheet. Generally, the smoother the carrier sheet the less of the mixture will be applied. Using as carrier sheet a paper of the type described above, the mixture preferably will be applied vto one face thereof so as to form thereon a layer Weighing between about 35 and 40V 50 parts by weight-Armeen HT (octodecylamine) 20 parts by'weight Black Toner (a carbon black Toner produced by Columbian Carbon Co., NzY.) 10 parts by weight English kaolin` 25 parts by weight tricresylphosphate The above mixturev is heated lso as jto be in flowable state and applied to the other facerof the carrier sheet to form thereon a layer weighing 10 gr./m.2.

I Example Il The carrier sheet and take-up layer are similar to those described in ExampleI. The transfer or dark layer consists of: i z i 22.5 parts by weight crude montanrwax 21.5 parts by weight petroleum jelly 24 parts by weight mineral oil II (Engler viscosity 2 at (semi-reinforcing furnacecarbon-black) Y 5 parts by Weight kaolin 10 parts by weight Abitolthydroabietil alcohol-#Hercules Powder) This mixtureis, applied=sovas to forma layer on one faceV of the carrier sheet weighing between 12 and 22 gr./m.2.

The above formula can be improved by the incorporai tion vof about 32.5% instead of 22.5%. of crude montan Wax, whereby the pressure-transferred indicia will appear more clearly and sharply defined andthe layer will be more resistant against smearing.

Example III Thecorrecting sheet comprises a` carrier' sheet of Perkallin (a filled or partially transparent artificial parchment paper such asonionskin paper) paper'weighing 40 37.50 parts by weight titanium dioxide 13.50 parts by weight lithopone zinc sulfide) 2.10 parts by weight Cereclor 42 (chloroparaihn42% chlorine 1.05 parts by weight Myverol 18-07 (glyceride of hy-V dratedlard) The dark, or transfer, layer is formed of a mixture, of

7 0.80 part by weight Palatinol AH (diocthlphthalate) 20.80 parts by weight ethanol 94% The thus formed mixture is finely ground and thereafter mixed under stirring with a solution consisting of:

3.50 parts by weight solution of 10% ethylcellulose N 100 in 90% ethanol 3.20 parts by'weight butyl Cellosolve stearate 1.20 parts by weight Lucite 44 (Du Pont-acryl) 25.00 parts by weight trichloroethylene 10.25 parts by weight Mark II A The thus formed mixture is applied to the carrier sheet so as to form on one face thereof a layer weighing 25 gr./m.2.

The dark transfer layer is formed by mixing:

50 parts by weight Armeen HT 20 parts by weight Black Toner parts by weight Palatnol C (dibutylphthalate) parts by weight castor oil 10 parts by weight English lkaolin The thus formed mixture is applied to the other face of the carrier sheet so as to form thereon a layer weighing between 5 and 7 gr./m.2.

Example IV The carrier sheet and the take-up layer are the same as described in Example I.

The dark transfer layer is formed by mixing two-solutions, namely a solution A which is formed of:

20 parts by weight Crilat D l3l (a 50% aqueous emulsion of methacrylate produced by Montecatini) 20 parts by weight Palatinol C (dibutylphthalate BASF) 500 parts by weight ethanol 94% 5 parts by weight ammonium hydroxide 28 Be Solution B" consists of:

400 parts by weight ethanol 94%, and 850 parts by weight of a paste C having the following composition Paste C is an intimate mixture of:

2.50 parts by weight carbon black (Peerless Mark Il A) 14.00 parts by weight methylglycol (methyl Cellosolve) 39.00 parts by weight titanium dioxide (titanium white) 18.00parts by weight kaolin 13.00 parts by weight Palatinol C (dibutylphthalate) 13.50 parts byweight castor oil Paste C is produced by passing the above mixture 3 times through a three-roller refiner.

Solutions A and B are now intimately mixed under stirring so as to become homogenized and the thus formed mass is applied to one face to the, for instance, smooth calendered paper carrier sheet so as to form thereon a layer weighing between about 39 and 40 gr./m.2.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of copy correcting sheets differing from the types described above.

While the invention has been illustrated and described as embodied in a correctingv sheetY for copies produced without the interpositi'on of carbon papers, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore', such Iadaptations should and are intended to beV comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An assembly for correcting contact copy of the type formed by placing one sheet which is provided on Y one face with a transfer layer in face to face contact with another sheet which is provided with a take-up layer, with said transfer and take-up layers contacting eachother, and applying pressure to spaced portions of the other face of said one sheet so that corresponding portions of said transfer layer thereof will be transferred onto the take-up layer of said other sheet, in combination, a first sheet provided on one face with a transfer layer; a second sheet provided on one face with a take-up layer, said first sheet will upon application of pressure become detached from its carrier sheet and adhere to said take-up layer of said other sheet, said one face of said interposed correcting sheet being adjacent to said transfer layer of said one sheet and said other face of said correcting sheet being adjacent to said take-up layer of said other sheet.

2. vIn a method of correcting contact copy ofthe type formed by placing one sheet which is provided on one face with a transfer layer in face to face contact with another sheet which is provided with a take-up layer, with said transfer and take-up layers contacting each other, and applying pressure to .spaced portions of the other face of said one sheet so that corresponding portions of said transfer layer thereof will be transferred onto the take-up layer of said other sheet forming copy thereon, the steps of interposing between superposed transfer and take-up layers having said copy formed/.on said take-up layer a correcting sheet carrying on 4 one face a transfer layer which when superposed upon said face of said one sheet provided with a transfer layer will upon application of pressure become detached from said correcting sheet and adhere to said one sheet, and carrying on the other face a take-up layer, which when superposed upon said take-up layer of said other sheet' will upon application of pressure become detached from said correcting sheet and adhere to the take-up layer of said other sheet with said take-up layer of said correcting sheet facing said copy formed on said take-up layer of said Iother sheet and-said transfer layer of said correcting sheet facing said transfer layer of said one sheet; and applying spaced pressure corresponding to the configuration of said copy to said first and second sheet with said correcting sheet interposed therebetween so that portions of said transfer and take-up layers of said correcting sheet corresponding to said copy will be transferred to corresponding portions of said transfer and take-up layerscarrying faces of said one and of said other sheet, respectively, thereby obliterating said previously formed copy thereon and restoring said transfer and take-up layers of said one and of said other sheet to their previous condition.

3. A correcting sheet adapted for use in an assembly other sheet, said correcting sheet comprising, in combination, a carrier sheet provided on one face thereof with a coating of a detachable dark colored transfer material which when superposed upon said transfer layer of said one sheet will upon application of pressure become detached from said carrier sheet and will adhere'to said one sheet and restore said transfer layer thereof, and provided on its other face with a coating of a detachable light colored take-up material which when superposed upon said take-up layer of said other sheet will upon application of pressure become detached from said car-` contacting said take-up'layer 0f said other sheet and apsheet assembly, the portions of said faces of said one and said other sheet which are directed towards each other and to which said pressure is applied Will be Vcovered by corresponding portions of said respective coatings of said correcting sheet.

References Cited in the le of this patent UNITED STATES PATENTS 701,443 wilson June 3, 1902 1,845,568 Strawn Feb. 16,1932 2,168,098 Groak Aug. 1, 1,939 3,096,867. Kuhiman July 9, 1963 FOREIGN PATENTS 528,589 Great Britain Nev. 1, 1940 

1. AN ASSEMBLY FOR CORRECTING CONTACT COPY OF THE TYPE FORMED BY PLACING ONE SHEET WHIHC IS PROVIDED ON ONE FACE WITH A TRANSFER LAYER IN FACE TO FACE CONTACT WITH ANOTHER SHEET WHICH IS PROVIDED WITH A TAKE-UP LAYER, WITH SAID TRANSFER AND TAKE-UP LAYERS CONTACTING EACH OTHER, AND APPLYING PRESSURE TO SPACED PORTIONS TO THE OTHER FACE OF SAID ONE SHEET SO THAT CORRESPONDING PORTION OF SAID TRANSFER LAYER THEREOF WILL BE TRANSFERRED ONTO THE TAKE-UP LAYER OF SAID OTHER SHEET, IN COMBINATION, A FIRST SHEET PROVIDED ON ONE FACE WITH A TRANSFER LAYER; A SECOND SHEET PROVIDED ON ONE FACE WITH A TAKE-UP LAYER, SAID FIRST AND SECOND SHEETS BEING SUPERPOSED WITH SAID TRANSFER AND TAKE-UP LAYERS ADJACENT TO EACH OTHER; AND A CORRECTING SHEET INTERPOSED BETWEEN SAID SUPERPOSED FIRST AND SECOND SHEETS, SAID CORRECTING SHEET COMPRISING A CARRIER SHEET PROVIDED ON ONE FACE THEREOF WITH A FIRST LAYER WHICH WHEN SUPERPOSED UPON, SAID TRANSFER LAYER OF SAID ONE SHEET WILL UPON APPLICATION OF PRESSURE BECOME DETACHED FROM ITS CARRIER SHEET AND ADHERE TO SAID ONE SHEET, AND PROVIDED ON ITS OTHER FACE, WITH A SECOND LAYER, WHICH WHEN SUPERPOSED UPON SAID TAKE-UP LAYER OF SAID OTHER SHEET WILL UPON APPLICATION OF PRESSURE BECOME DETACHED FROM ITS CARRIER SHEET AND ADHERE TO SAID TAKE-UP LAYER OF SAID OTHER SHEET, SAID ONE FACE OF SAID INTERPOSED CORRECTING SHEET BEING ADJACENT TO SAID TRANSFER LAYER OF SAID ONE SHEET AND SAID OTHER FACE OF SAID CORRECTING SHEET BEING ADJACENT TO SAID TAKE-UP LAYER OF SAID OTHER SHEET. 